*related http://videosift.com/video/A-Light-That-Runs-On-Gravity-very-cool

A Light That Runs On Gravity has been added as a related post - related requested by eric3579.

I've seen this guys very early video when he was just forming the company and putting this device together. It had to have been quite some time ago and I imagine these things are widely available now. Nice to see it in action though. I love tech that gets us using less power.

Make it power a USB port and half the Raspberry Pi people will buy one.

Nice idea, although LEDs have an extremely low power draw. Not sure if the gravity plus gearing would generate enough watts for the Pi.

USB is 5 volts at usually under 1 amp (.5 amps for USB 2 and .9 for USB 3). So I think that suggests about a 2.5-5 watt draw for USB, although I could be wrong -- long time since I took any EE classes. With very quick googling, I'm not getting a concrete number on the wattage of the (single?) LED in the Gravity Light, but one result suggested in the milliWatt range (60-80mW). Same post says that a cheap hand crank generates about 1 watt with vigorous cranking that will wear out your arm/hand quickly.

So, I'm thinking that 2.5-5 watts would require a much more heavy-duty and less portable gravity-fed system. Very much doable (bicycle pedaling can generate 50 watts fairly easily), but probably only with more bulk than what can power LED lighting.

Their specs say the LED runs at 100mw on "high".

1kg falling 1m is roughly 2.5 mwh, so yeah, you'll need either a lot of a rocks or a long fall to run much more than an LED for very long. Even then they can't be losing too much if they can have it running for 20 minutes.

I suppose its also worth remembering that gravity is harnessed on a massive scale for the generation of electricity by dams, so yeah, in some parts of the world its quite possible your computer would be gravity powered.